1. Field of the Invention
The invention relates to sheet feed and sheet presenting assemblies.
2. Description of the Prior Art
Sheet feed assemblies are used in a wide variety of fields to feed sheets from a stack. Examples include banknote dispensing and also photocopy paper dispensing. A known system for dispensing sheets from a stack makes use of a vacuum feed device, such as a rotatable wheel through which suction is applied selectively to draw a sheet from a stack upon rotation of the wheel. Examples of such devices are disclosed in U.S. Pat. No. 3,041,067, DE-A-3921582, and EP-A-0413471. In these assemblies, it is important to prevent sheets from inadvertently being fed or two sheets being fed at once. This problem is addressed in U.S. Pat. No. 3,041,067, for example, by providing an auxiliary holding device upstream of the vacuum feed device, to which vacuum is supplied. In use, vacuum is supplied both to the holding device and to the vacuum feed device, the vacuum force at the holding device being higher so that no sheets are fed. When it is desired to feed a sheet, pressure is additionally supplied to the holding device to reduce the overall vacuum force allowing a sheet to be drawn away.
A similar arrangement utilizing an additional holding device is described in DE-A-3921582. In this case, when the feed device has seized a sheet and starts to pull it away, the suction applied to the holding device is temporarily shut off so that the sheet can be removed.